Matthew Sinkiewicz was a sergeant with the Southeastern Pennsylvania Transportation Authority (SEPTA) Police Department before being fired earlier today. He was fired for bashing two protesters with a baton back on May 30th. He had been on paid administrative leave since then. A criminal investigation is still ongoing.
This was not the first time that Sgt. Sinkiewicz has been disciplined. In 2016 he body slammed a handcuffed black man that he had arrested for disorderly conduct. SEPTA concluded that he was at fault for how he handled the man. He was also cited for violating the department's body camera policy because he conveniently "forgot" to turn on his body camera before engaging in contact with the victim (https://6abc.com/septa-transit-police-officer-disciplined-arrest/1410421/).